This disclosure relates generally to systems for controlling the humidity of intake air supplied to an internal combustion engine, and more specifically to systems for dehumidifying engine intake air.
Differing levels of specific humidity in the atmosphere are known to impact the operation of internal combustion engines generally, and of spark-ignited engines in particular. For example, in spark-ignited, natural gas engines, increased levels of specific humidity tend to slow combustion by decreasing heat release rates and also by increasing the duration of individual combustion events.
Heretofore, systems have been devised to compensate for such adverse humidity effects by manipulating one or more engine operating parameters. It is desirable to alternatively control humidity of the air entering the engine such that the humidity of the engine intake air is maintained near a target humidity value.
The present invention may comprise one or more of the following features or combinations thereof. An intake air dehumidification system for an internal combustion engine may comprise an intake conduit having one end coupled to an intake manifold of the engine and an opposite end configured to receive ambient air and a peltier junction device responsive to at least one control signal to cool, and therefore condense moisture from, ambient air supplied by the intake conduit to the intake manifold. Means may be provided for determining a specific humidity value corresponding to specific humidity of the ambient air supplied to the intake manifold, and a control circuit may be provided to produce the at least one control signal as a function of the specific humidity value to maintain the specific humidity of the ambient air supplied to the intake manifold near a target humidity value. The system may further include means for dissipating the moisture condensed from the ambient air by the peltier junction device.
The means for determining a specific humidity value may include a temperature sensor positioned downstream of the peltier junction device and producing a temperature signal indicative of the temperature of the ambient air entering the intake manifold, a pressure sensor positioned downstream of the peltier junction device and producing a pressure signal indicative of the pressure within the intake manifold, and a relative humidity sensor positioned downstream of the peltier junction device and producing a relative humidity signal indicative of the relative humidity of the ambient air entering the intake manifold, wherein the control circuit is configured to produce the specific humidity value as a function of the temperature signal, the pressure signal and the relative humidity signal. The control circuit may include a closed-loop control strategy configured to produce an error value as a difference between the target humidity value and the specific humidity value, and to produce the at least one control signal in a manner that minimizes the error value. For example, the control circuit may include a controller responsive to the error value to produce the at least one control signal. Alternatively, the control circuit may include a table mapping error values to corresponding control signal values, the table responsive to the error value to produce the at least one control signal.
Alternatively, the means for determining a specific humidity value may include a temperature sensor positioned upstream of the peltier junction device and producing a temperature signal indicative of the temperature of the ambient air entering the intake conduit, a pressure sensor positioned upstream of the peltier junction device and producing a pressure signal indicative of the pressure of ambient air entering the intake conduit, and a relative humidity sensor positioned upstream of the peltier junction device and producing a relative humidity signal indicative of the relative humidity of the ambient air entering the intake conduit, wherein the control circuit is configured to produce the specific humidity value as a function of the temperature signal, the pressure signal and the relative humidity signal. For example, the control circuit may include an open-loop control strategy configured to produce an error value as a difference between the target humidity value and the specific humidity value, and to produce the at least one control signal as a function of at least the error value. The system may further include a mass air flow sensor producing a mass air flow signal indicative of the mass flow of air past the peltier junction device, wherein the open-loop control strategy is further configured to produce the at least one control signal as a function of a product of the error value and the mass air flow signal.
In either case, the system may further include a turbocharger having a compressor defining a compressor inlet configured to receive ambient air and a compressor outlet fluidly coupled to the opposite end of the intake conduit, wherein the peltier junction device is positioned downstream of the compressor outlet. Alternatively, the peltier junction device may be positioned upstream of the compressor inlet.
The peltier junction device may define a cooling side and a heating side, and the system may further include a first heat transfer structure mounted to the cooling side of the peltier junction device and disposed in the flow path of the ambient air supplied by the intake conduit to the intake manifold, with the cooling side of the peltier junction device and the first heat transfer structure cooperating to cool, and therefore condense moisture from, the ambient air supplied by the intake conduit to the intake manifold. The system may further include a second heat transfer structure mounted to the heating side of the peltier junction device and configured to direct heat away from the heating side of the peltier junction device.
The intake conduit may include first and second separate airflow passages with the peltier junction device mounted therebetween with the cooling side in fluid communication with the first airflow passage and the heating side in fluid communication with the second airflow passage. The first airflow passage may have one end coupled to the intake manifold downstream of the peltier junction device and an opposite end configured to receive ambient air upstream of the peltier junction device, and the second airflow passage may have one end configured to receive ambient air upstream of the peltier junction device and an opposite end vented to ambient downstream of the peltier junction device.
Alternatively, the peltier junction device may be mounted to the intake conduit with the cooling side in fluid communication with ambient air flowing through the intake manifold and with the heating side in fluid communication with ambient.
The system may further include a moisture collection structure configured to collect moisture condensed from the ambient air supplied by the intake conduit to the intake manifold and to direct the collected moisture away from the ambient air supplied by the intake conduit to the intake manifold. The moisture collection structure may be configured to direct the collected moisture from the cooling side of the peltier junction device to the heating side of the pelter junction device. The moisture collection structure may extend from the first heat transfer structure at least to the second heat transfer structure to direct the collected moisture from the first heat transfer structure toward the second heat transfer structure. The moisture collection structure may comprise at least one moisture absorbent member mounted to the first heat transfer structure and extending through the second heat transfer structure, the moisture absorbent member absorbing moisture condensed by the cooperation of the cooling side of the peltier junction device and the first heat transfer member and directing the absorbed moisture toward the second heat transfer structure for evaporation by the ambient air flowing past the second heat transfer structure.
An intake air dehumidification system for an internal combustion engine may comprise an intake conduit having one end coupled to an intake manifold of the engine and an opposite end configured to receive ambient air and a peltier junction device responsive to a number of control signals to cool, and therefore condense moisture from, ambient air supplied by the intake conduit to the intake manifold. Means may be included for determining a specific humidity value corresponding to specific humidity of the ambient air downstream of the peltier junction device, and a control circuit may be provided to produce the number of control signals as a function of the specific humidity value to maintain the specific humidity of the ambient air supplied to the intake manifold near a target humidity value.
The control circuit may include means for producing an error value as a difference between the target humidity value and the specific humidity value, and means for producing the number of control signals in a manner that minimizes the error value. The means for producing the number of control signals in a manner that minimizes the error value may include a controller producing a number of pulse width modulated output signals, and a driver circuit responsive to the number of pulse width modulated output signals to produce the number of control signals. The controller may control the pulse widths of the output signals as a function of the error signal to control the on-times of a corresponding number of peltier junction elements forming the peltier junction device.
The peltier junction device may include a number of peltier junction elements. The means for producing the number of control signals in a manner that minimizes the error value may include a table mapping error values to subset values corresponding to subsets of the number of peltier junction elements, means responsive to the subset values to enable corresponding subsets of the number of peltier junction elements for operation, and a driver circuit supplying the control signals to each of the enabled peltier junction elements to activate each of the enabled peltier junction elements.
An intake air dehumidification system for an internal combustion engine may comprise an intake conduit having one end coupled to an intake manifold of the engine and an opposite end configured to receive ambient air, and a peltier junction device responsive to a number of control signals to cool, and therefore condense moisture from, ambient air supplied by the intake conduit to the intake manifold. Means may be provided for determining a specific humidity value corresponding to specific humidity of the ambient air upstream of the peltier junction device, and a mass air flow sensor may be provided for producing a mass air flow signal indicative of the mass flow of air past the peltier junction device. A control circuit may be included to produce the number of control signals as a function of the specific humidity value and the mass airflow signal to maintain the specific humidity of the ambient air supplied to the intake manifold near a target humidity value.
The control circuit may include means for producing an error value as a difference between the target humidity value and the specific humidity value, and means for producing the number of control signals as a function of a product of the error value and the mass air flow signal.
The peltier junction device includes a number of peltier junction elements, and the means for producing the number of control signals in a manner that minimizes the error value may include a table mapping error values to subset values corresponding to subsets of the number of peltier junction elements, means responsive to the subset values to enable corresponding subsets of the number of peltier junction elements for operation, and a driver circuit supplying the control signals to each of the enabled peltier junction elements to activate each of the enabled peltier junction elements.
These and other objects of the disclosure will become more apparent from the following description of the illustrative embodiments.